There is limited and inconclusive evidence regarding the association between maternal dietary macronutrients (carbohydrate, protein and fat) and birth outcomes. The central aim of this project was to study maternal macronutrient dietary intakes through the generation of a unique maternal weight gain dietary pattern and its relationship to birth outcomes.
Analyses were conducted in three birth cohorts such as the CAffeine and REproductive Health study (CARE) in the U.K (N=1196), The Norwegian Mother and Child Cohort Study (MoBa) (N=85,574) in Norway and The Danish National Birth Cohort Study (DNBC) (N=63,755) in Denmark. The birth outcomes of interest were birthweight, and odds of small-for-gestational-age (SGA) and large-for-gestational-age (LGA) babies.
The thesis undertook a random-effects meta-analysis of three birth cohorts (N= 149,927 mother-infant pairs) to explore the association between maternal dietary macronutrient intakes and birth outcomes. The results showed an additional increment of 30g/day in dietary protein during pregnancy was associated with higher birthweights (20g, 95% CI 10g to 31g; I2= 38%, combined p value<0.001) but, not with the odds of SGA and LGA babies.
Further, in MoBa, maternal dietary patterns were explored using principal component analysis (PCA). The results found that high “marine food” dietary pattern scores were associated with higher birthweights (5g; 95% CI 2g to 9g; p=0.005), and lower odds of SGA delivery (0.95; 95%CI 0.93 to 0.97; p<0.001), but not with LGA delivery. Also, high adherence to an “animal meat” dietary pattern was associated with a lower birthweight (-5g; 95%CI -9g to -1g; p=0.02) and higher odds of LGA delivery (1.06; 95% CI 1.04 to 1.09; p<0.001).
Furthermore, a unique set of gestational weight gain dietary patterns (GWGDP) were created in MoBa and DNBC using reduced rank regression (RRR) and included four risk factors. Based on previous literature from large systematic reviews, the four risk factors included for a analyses were total energy intake, smoking habits, pre-pregnancy BMI and physical activity. In MoBa, the results demonstrated that a high “fish and coffee” GWGDP score was associated with higher birthweight (6g; 95% CI -1g to 11g; p=0.01) and lower odds of LGA delivery (0.95, 95%CI 0.92 to 0.98; p<0.003). Further, high adherence to “animal meat and sugar-sweetened beverages (SSB)” dietary pattern in MoBa and “meat” dietary pattern in DNBC were associated with higher odds of LGA delivery (1.03, 95%CI 1.01 to 1.05; p<0.001) and (1.16; 95%CI 1.12 to 1.21; p<0.001), respectively.
In summary, this thesis found that no particular macronutrient appears to be associated with poorer birth outcomes such as odds of SGA and LGA babies within a well-nourished group of pregnant women. Therefore, macronutrient composition, as stated in the dietary reference values (DRVs), is still warranted for optimised growth of the offspring. However, additional weight gain through excess energy intakes from protein and carbohydrate should be avoided.
